Wireless Service Providers (WSPs) offer various wireless service models to their subscribers. Many of these service models are dictated by regulations. For example, most WSPs in the United States offer service contracts with preconfigured roaming agreements and mobile devices that are locked. A locked mobile device prevents a subscriber from using the mobile device on other WSP networks.
Most mobile devices sold in the United States are pre-locked by the WSP. Nearly all WSPs subsidize the price of mobile devices in exchange for voice/data service contracts. Recently, some unlocked mobile devices, such as smartphones, are being sold for a much higher price without the subsidy. Many subscribers are willing to pay a premium price for an unlocked device, while others choose, as is more commonly the case, to unlock their device through the use of software tools, without the permission of the WSP. In response to the use of such software tools, more WSPs are offering subscribers the option to unlock their device, often for a fee, even though it means a subscriber can use that phone with another WSP. Some WSPs unlock devices after a subscriber's account has been active for a specific time period or the service contract term has been fulfilled. Other WSPs may offer to unlock the subscriber's mobile device while a service contract is active, depending upon the details of the subscriber's service contract.
One method WSPs use to unlock mobile devices is sending an unlock code with step-by-step instructions to the subscriber's mobile device. Another method WSPs use to unlock mobile devices is asking a subscriber to send his or her mobile device to the WSP for unlocking. Yet another method WSPs use to unlock mobile devices is providing kiosks that are configured with software to unlock the mobile device.
The present device locking model that many WSPs use can cause major inconveniences when the subscriber travels to foreign countries and, particularly, foreign countries in which the subscriber's home WSP has no roaming agreements with a foreign WSP. Under these circumstances, the only choice for the subscriber is to purchase a prepaid mobile device or prepaid SIM (Subscriber Identity Module) in the foreign country. This creates a few potential problems. For example, the subscriber can no longer invoke all services to which he or she is subscribed in their home wireless network, and the subscriber is encumbered with having to carry multiple mobile devices with cellular access being available only through the prepaid mobile device.
An advantage to the subscriber of having an unlocked mobile device is the ability for the unlocked mobile device to be used in countries other than the subscriber's home country, often at a fraction of the cost of buying a local prepaid SIM card. Otherwise, the subscriber is left paying high international roaming fees.
In 2G networks, the SIM card and SIM application are bound together, so that the common phrase “SIM Card” is a physical circuit card with the SIM application, In 3G networks, a UICC (Universal Integrated Circuit Card) is used. A UICC ensures the integrity and security of a subscriber's personal data. The memory capacity of a typical UICC is a few hundred kilobytes, although the memory capacity of UICCs is increasing due to the number of applications that need to be stored in the UICC. For example, a UICC may contain a USIM (Universal SIM) application for UMTS (Universal Mobile Telecommunications System) networks, a CDMA (Code Division Multiple Access) SIM (CSIM) for CDMA networks, and a SIM application for GSM (Global System for Mobile communications) networks, making it possible for the same UICC to provide access to different 2G and/or 3G networks.
When a subscriber is in a foreign country and attempts to make a call, the subscriber has a few options. If there is no roaming agreement established between the local WSP(s) and the home WSP, the subscriber is unable to use his or her mobile device to make the call. In this case, the subscriber can purchase a prepaid mobile device with a new SIM card that is configured to provide cellular access in the foreign country. This scenario presents a few problems. If the country or the area the subscriber is visiting is unsafe, the subscriber may not want to venture out in public to purchase a new mobile device for worry of their personal safety. Also, it is inconvenient for the subscriber to purchase another mobile device to be used only locally in the foreign country. If the subscriber is staying for a short time in a foreign country, buying a locally-compatible mobile device may not be practical, financially or otherwise. Likewise, if the subscriber is traveling to several foreign countries, and stopping in each country for only a few days or perhaps even longer, buying a locally-compatible mobile device for each country may not be a feasible communications solution.
If, however, there is a roaming agreement between the local service provider and the home WSP, the mobile device will permit the subscriber to make the call and the bill will be settled between the two WSPs. Prior to the roaming service being authorized, the subscriber will be authenticated by the home WSP. For prepaid roaming agreements, the call-related data must be exchanged in real-time between the local WSP and the home WSP by using a special CAMEL (Customized Applications for Mobile networks Enhanced Logic)-based platform, to prevent the balance of the roaming subscriber's account from becoming overdrawn.